according to what they've written in 9D official site, i think we need to meet the below conditions to change the char name...
1. purchase inventory must be empty
2. screenshot all friends from FL to add again after the char name has changed
so, i guess they just create the new char with the name u want and put this char to ur current account after removing the old char. its like replacing the old char with the new name char in same account.
my advice to those who's gonna try this:
- take screenshots of lvl, stats and items in all bags/storage just in case if something is missing and if the new char doesn't match with the old one's stats, lvl, % of current exp, etc,..